1. Field of Invention
This invention relates generally to devices for regulating the flow of liquids, and particularly relates to a flow divider for dividing a stream of liquid, such as liquid fuel, into two or more smaller streams of liquid or to a pump for pumping a single flow of liquid to one or more locations in substantially accurate flow rates.
2. Description of Related Art
When working with liquids, it is often desirable to divide a single stream of liquid into several smaller, preferably equal streams of liquid or several substantially accurate streams of liquid. This is typically done using a fluid metering device such as liquid flow divider, an equal-flow pump, or an equal-flow liquid motor.
A typical prior art liquid flow divider is taught in U.S. Pat. No. 4,531,535 to Kiernan. As shown in FIG. 4 of Kiernan, such liquid flow dividers typically include multiple dividing units of two intermeshed spur gears. The various dividing units are typically linked together by a drive train that may include a drive line, drive shafts, or a sun gear. As a result of this linkage, all of the gears within the various dividing units rotate at substantially the same speed.
Within each individual dividing unit, a liquid inlet port is positioned on one side of the intermeshing portion of the pair of spur gears, and a liquid discharge port is positioned on the other side of the intermeshing portion of the pair of spur gears. A housing is provided that conforms to the exterior portions of the spur gears that are not in communication with the liquid inlet port or the liquid discharge port. All of the various dividing units' liquid inlet ports are in communication with a single, pressurized liquid source.
In operation, pressurized liquid from the pressurized liquid source first enters each dividing unit's liquid inlet port. The pressurized liquid then causes the gears in each dividing unit to rotate in opposite directions so that each gear's teeth carry liquid from the liquid inlet port, around the exterior portion of the gear, and into the liquid discharge port. Because all of the dividing gears within the liquid flow divider are preferably the same size and shape, and because the gears are linked together by a central drive train so that all of the gears rotate at the same rate, the flow rate of liquid around each of the flow divider's various gears is identical to the flow rate of liquid around each of the flow divider's other gears. Accordingly, because each dividing unit contains two gears of substantially the same size that convey liquid from the dividing unit's liquid inlet port to the dividing unit's liquid discharge port, liquid flows through each dividing unit at a rate that is equal to two times the rate at which the liquid flows around a single gear.
Accordingly, prior art liquid flow dividers are typically designed to include one dividing unit for each equal discharge stream that the flow divider is to produce. For example, if the flow divider is to produce 10 equal discharge streams of liquid, the flow divider will include 10 separate dividing units. The liquid fuel entering the flow divider normally enters at an elevated pressure relative to ambient conditions. Then it exits the flow divider normally at a discharge line pressures that are lower than the inlet pressure since energy is lost in making the gears rotate. This elevated pressure inside the flow divider exerts forces on the housings of the dividing units that are proportional to the difference between the pressure inside the flow divider and ambient pressure outside the flow divider. This force on the housing can, when the difference in pressure is high enough, cause the housings to expand, change shape, and deform, and detrimentally affect the diving units' metering efficiency or impair their rotation.
Flow dividers have been developed that did away with this deformation of the dividing units by enclosing them inside a pressurized plenum. The pressure plenum would contain the high pressure of the fuel, and be subjected to the large forces resulting from the difference between the liquid pressure inside the flow divider and ambient atmospheric pressure outside. The dividing units themselves would be subjected to only the much smaller pressure differences generated by the liquid passing through them. This type of flow divider, usually denoted a “circular flow divider”, has the dividing units arranged in a circular array around a central timing gear or sun gear. This timing gear intermeshes with the innermost gears in all dividing units to synchronize and cause all dividing units to always rotate at the equal speeds. A large, circular housing or plenum contains all of these dividing units and functions as a pressure vessel. The liquid fuel enters the flow divider through a port or ports in this circular housing and fills its volume so as to submerge the dividing units. The pressurized liquid fuel is forced into each dividing unit through an inlet port hole in each one.
U.S. Pat. No. 6,857,441 to Flavelle (“Flavelle”) solved some problem of the earlier art by providing a pressure balance inlet port and a pressure balance discharge port adjacent an exterior portion of each end gear within a series of gears for balancing forces exerted on the end gear by liquid passing through the various inlet and discharge ports. However, there continues a need for improved liquid flow dividers, and other fluid metering devices, that are more robust and that take up less space than prior art fluid metering devices.
All references cited herein are incorporated herein by reference in their entireties.